Damper valve for hydraulic power steering device

Abstract

A damper valve for a hydraulic power steering device is disposed in a hydraulic oil circuit connecting an oil passage changing-over valve in a gear box and left and right oil chambers of a power cylinder. It is provided with a piston valve which is opened by through-flow of hydraulic oil returned back to the oil passage changing-over valve from either one of the left and right chambers of the power cylinder, and a check valve which is disposed in a valve body of the piston valve and which allows only hydraulic oil supplied from the oil passage changing-over valve to either one of the left and right chambers of the power cylinder to flow through the check valve. The piston valve is structured such that a throttle oil passage is formed by through flow of the returned hydraulic oil having an oil pressure of a predetermined value or less, and a fully opened oil passage is formed by through flow of the returned hydraulic oil having an oil pressure of more than the predetermined value. Oil passages for the returned-back hydraulic oil are formed in the valve body of the piston valve.

What is claimed is: 
     
       1. A damper valve for a hydraulic power steering device which is disposed in a hydraulic oil circuit connecting an oil passage changing-over valve in a gear box and left and right oil chambers of a power cylinder, the damper valve comprising a piston valve which is arranged and constructed to be opened by through-flow of hydraulic oil returned back to the oil passage changing-over valve from either one of the left and right chambers of the power cylinder, and   a spring which closes the piston valve, and   a check valve which is disposed in a valve body of the piston valve and which is arranged and constructed to allow only hydraulic oil supplied from the oil passage changing-over valve to either one of the left and right chambers of the power cylinder to flow through the check valve,   wherein the piston valve opens against biasing force of the spring, and is arranged and constructed such that a throttle oil passage is formed by through-flow of the returned hydraulic oil having a predetermined oil pressure or less and a fully opened oil passage is formed by through-flow of the returned-back hydraulic oil having more than the predetermined oil pressure, and   a passage of the returned-back hydraulic oil disposing around diametrical direction of the check valve disposed portion, inside of the valve body of the piston valve and the spring is housed in the passage of the returned-back hydraulic oil.   
     
     
       2. A damper valve for a hydraulic power steering device according to claim 1, wherein oil passages for the returned hydraulic oil are formed in the valve body of the piston valve. 
     
     
       3. A damper valve for a hydraulic power steering device according to claim 1, wherein a clip holds the check valve, fixed on the disposed portion of the check valve, inside of the valve body of the piston valve. 
     
     
       4. A damper valve for a hydraulic power steering device according to claim 1, wherein a socket disposed on an end part of a pressure pipe of hydraulic oil extending from the power cylinder, is connected to a casing forming an oil passage change-over valve accommodating portion of a gear box, and the damper valve is assembled in the casing.